Bacterial contamination of waterways, both in the United States and abroad is a continuing problem which frequently generates newspaper headlines. Any program to keep water clean is dependent on providing an effective monitor for water quality including low levels of microbial and chemical contaminants. While technologies are emerging for the rapid analysis of samples containing cellular and sub-cellular material such as DNA and RNA, the means for sampling the water to collect the biological and chemical fragments have not progressed as rapidly.
One prior art method, known as "grab sampling" is merely the collection of an instantaneous unit of water matrix in a sampling vessel such as a glass jar. However, a grab sample is often inadequate to characterize a dynamic water body such as a stream or river where flow patterns and content change rapidly and frequently.
While automatic devices exist for sampling water, these typically have the disadvantage of not being man-portable. One reason for this is that such devices frequently include one or more containers for storing sampled water, which add to the weight and space occupied by the device. Another disadvantage of some prior art devices is that they are designed to take only a single time-limited sample. In view of the changing conditions of rivers and streams over time, it is desirable to have a device which can take a large number of samples over a relatively long period of time (e.g. two weeks) without human intervention.
Still another disadvantage of some prior art is their need to use a high-pressure or high-capacity pump to generate the liquid flow demanded by the sampler cartridge. This requires generally higher voltage and ultimately higher power requirements not readily available by battery power alone. It is desirable to have a sampler capable of sampling in remote areas autonomously (i.e., without an external source of power).
U.S. Pat. No. 5,844,147 is directed to a water sampling apparatus in which a sample is collected at a relatively high flow rate and then is temporarily stored in a storage container under pressure before passing through a solid phase extraction device at a slower rate which corresponds to the flow tolerance of the extraction device. This enables a quantity of water to be sampled over a single limited time frame during which the storage container fills up. The apparatus does not include a backflush capability which would be necessary to keep the flow system clear for providing repetitive samples.